Heme oxygenase (HO) catalyzes the oxidative cleavage of heme to biliverdin with production of CO and release of the chelated Fe3+. Although much is known about the function, multiplicity and regulation of the mammalian and algal heme oxygenase systems, practically no attention has been given to the heme oxygenases in insects. I proposed to study for the first time heme oxygenase in an invertebrate animal. The long term goal of the proposed research project is to fill a gap in our knowledge of heme metabolism in blood feeding insects. The results obtained will define the role of heme oxygenase in iron re-utilization and homeostasis in mosquitoes. They will provide a tool to study the fate of heme in hematophagous insect vectors of disease, and may lead to the design of novel and effective ways to control insects of medical importance. The specific aims of the project are: 1. To clone and characterize HO cDNA(s) from the mosquito A. aegypti. Using D. melanogaster HO molecular probes (cDNA, antibodies) we will screen for similar HO cDNAs in A. aegypti. These will be sequenced and the structure of the deduced protein(s) will be determined. 2. To express, purify and characterize A. aegypti heme oxygenase protein(s). Using a heterologous expression system, A. aegypti heme oxygenase(s) will be partially characterized and compared to other heme oxygenases. The recombination protein will be used for production of polyclonal antibodies. 3. To determine the expression pattern of A. aegypti heme oxygenase(s) during the development, in different organs, and after blood feeding Using northern and western blotting techniques, the expression of A. aegypti HO mRNA(s) and protein(s) will be studied at different developmental stages and in female mosquitoes before and after a blood meal. The organ specific expression will be studied in larvae and in female mosquitoes at various stages before and after blood feeding.